iOS simply means the operating system that runs on Apple mobile devices.

iOS = iPhone Operating System It is the software that powers devices like the iPhone, iPad (though iPads now use iPadOS), and older iPod Touch devices. It is developed by Apple Inc..

In simple terms:

iOS is what makes your phone work — it controls things like:

Apps (WhatsApp, Instagram, etc.) Touchscreen actions Notifications Settings and security

Example:

When someone says “iOS 17”, they mean version 17 of Apple’s mobile software, with new features and updates.